The invention concerns an analog-digital converter for the evaluation of the output signal of an optoelectronic sensor element wherein an inverter is provided having a switching transistor with a series connected load element, and a further transistor is provided which connects the sensor element to an input of the inverter.
Such an analog-digital converter is described in German patent application No. P 2,838,647.2 corresponding to U.S. application Ser. No. 069,788. It there consists of a converter, the input of which is connected on the one side via a series connection of two switching transistors with a supply voltage source, and on the other side via a third switching transistor with the output of an optoelectronic sensor element. When the charge which is optically generated in the sensor element within an integration time determined by the third switching transistor has attained a predetermined reference value, then the converter proceeds into a switching state in which at its output, a logic signal "1" can be obtained. In the case of non-attainment of the reference value, the converter remains in a state in which the logic output signal "0" is present. The converter and one of the two switching transistors which lie in series represent circuit parts of a shift register stage which is individually associated with the sensor element. An analog digital converter for the evaluation of the analog output signals of a linear image sensor is further referred to in the prospectus 77144 of the firm Reticon Corp., Sunnyvale, Calif., wherein the "Model LC 600 Digital Line Scan Camera" is specified. If one of the output signals of the consecutively scanned or interrogated sensor elements exceeds a predetermined threshold value, then a logic "1" is released via the converter. The next following output signal of a sensor element which does not attain the threshold value, on the other hand, results in the switchover of the converter to an output signal which corresponds to a logic "0."